In the field of multiple station transfer machines, there exist two fundamentally different methods of transferring or moving a workpiece from station to station. In one method, a workpiece (or workpieces) is clamped in a pallet and the pallet is transferred from the station and is located and clamped in each station, thereby establishing the position of the workpiece with respect to each particular station. Techniques for the locating and clamping of such pallets are illustrated by my U.S. Pat. Nos. 4,201,284 and 4,362,233. Machines utilizing this technique are generally referred to as pallet machines. They are generally applied to workpieces whose configurations are such as to make it difficult to transfer and relocate the workpiece without benefit of a pallet.
However, there are some types of workpieces, for example, cylinder heads for internal combustion engines, in which it is possible to transfer the workpieces from station to station as independent workpieces, without their being clamped in a pallet. Such machines are referred to as free part transfer machines. In machines of this type, it is present normal practice to locate and clamp the workpieces in each station using separate hydraulically actuated mechanisms.
It is one object of this invention to provide a standard rotary actuated mechanical clamp module usable in free part transfer machines which can be used in a variety of clamping applications, and adapted to be driven by a single actuating means on a multiple station machine.
It is another object of this invention to provide, in the aforesaid mechanical clamp module, optional means for actuating the locating system for the workpiece in each station in the appropriate time relationship with the clamping system.
It is a further object to provide a preloaded spring in the force application system with alternate conditions of wind-up and wind-down adaptations to balance loading on the common actuator extending to the multiple stations.
In the general case, it is necessary for the workpiece clamps to be retracted several inches from the workpiece for the workpiece to be transferred into and out of a given station. As the clamps approach the workpiece, during the initial portion of a clamp operation, little force is required to move the clamps. However, once the clamps contact the workpieces, a large clamping force is required to hold properly the workpiece during the processing operation performed in any given station. It is another object of this invention to provide a mechanism which has a relatively low mechanical advantage from input to output during the inital portion of the clamp operation, then have a relatively large mechanical advantage from the input to output during the actual clamp portion of the operation.
Since it is intended that a single actuation mechanism be utilized to operate a multiplicity of mechanical clamp modules, it is very desirable that the mechanical efficiency of each unit be very high. It is another object of this invention to provide a mechanism in which the aforesaid movement objectives are met utilizing only high frequency mechanisms.
In my copending U.S. patent application, Ser. No. 327,517, filed Dec. 4, 1981, now U.S. Pat. No. 4,498,572, issued Feb. 12, 1985, a clamping system having substantially identical objectives has been disclosed. Whereas in that system, these objectives were achieved with a mechanism requiring a linear input motion operating parallel to the line of stations of a multiple station transfer machine, in this present invention the clamping system, in the various stations, is operated through the rotation of a shaft also operating parallel to that line of machine stations. The use of a rotating shaft, as opposed to the use of a linear motion, permits closer spacing of the clamp modules, and creates no expanding or contracting reaction forces between the machine stations, which is advantageous in many applications.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable persons skilled in the art to practice the invention, all in connection with the best mode presently contemplated for the invention.